Flood prevention measures need closer monitoring

Natural measures to manage river flooding can play a valuable role in flood prevention, but a lack of monitoring means their true potential remains unclear, researchers say.

A team of
experts, including Professor Joseph Holden at the University of Leeds, has
compiled the evidence on natural flood management in the UK, in order to better
inform policy decisions and show where crucial gaps in knowledge lie.

The authors say
natural measures have proved useful at preventing flooding after minor
rainstorms, and can be a worthwhile component of a larger package of flood
prevention measures.

For measures such as tree planting which aim to change the
way rainfall runs off the land, the evidence of the impact on flooding is
mixed.

Meanwhile,
measures to restore natural floodplains by making room for the river, for
example by removing flood walls and other obstacles, have been shown to reduce
flood water levels.

Natural flood
management is an area of increasing interest for policy makers, but its
implementation can present a complex balancing act between the needs of
different groups, including the public, farmers and land owners.

Mixed messages
about the efficacy and scalability of natural flood management measures add to
the uncertainty surrounding their benefits.

Professor
Holden is Director of water@leeds and leader of the Natural Environment
Research Councils Integrated Catchment Solutions Programme (iCASP) at the Universitys School of Geography.

He said: The 2015
Boxing Day floods proved yet again the cost and the danger of extreme floods in
the UK. Reactionary measures to prevent flooding may not provide the defences
needed as climate change continues to affect our weather and instances of
extreme flooding increase.

We need
collaborative approaches to build knowledge and evidence to support the use of
natural flood management as part of wider integrated solutions.

"Programmes such as iCASP that involve joined-up thinking and planning across all aspects of river
catchment systems will be invaluable in evaluating and establishing the best
possible strategies for flood management.

The review and
assessment of scientific evidence about natural flood monitoring came from a
variety of sources, ranging from field data to model projections and expert
opinion. The findings are published today in Proceedings of the Royal Society.

Lead author Dr
Simon Dadson at the University of Oxford said: What weve found is that when
it comes to natural flood management, there are some interventions for which
there is very strong evidence, but these tend to be in small-scale river
catchments.

"One of the main problems decision-makers face is that differences
between catchments make it difficult to transfer evidence from one location to
the other  and we dont yet know whether the effects in small catchments can
be extrapolated to larger ones.

Dr Dadson
added: Our message to Defra and the Environment Agency is that they need to
establish more systematic large-scale surveys and monitoring programmes, and
feed natural flood management into planning at the catchment scale.

Its also
really important that catchment-based schemes that have been instigated by
communities and local wildlife or river trusts are monitored and evaluated so
that the right lessons can be learned for the future.

The full paper, A restatement of the natural science
evidence concerning catchment-based natural flood management in the United
Kingdom, is published in Proceedings of the Royal Society 15 March 2017.